This report shows that in the Gulf of California fisheries landings are positively related to the local abundance of mangroves. Mangroves are disappearing rapidly worldwide despite their well-documented biodiversity and the ecosystem services they provide. Failure to link ecological processes and their societal benefits threaten mangroves and result in costly "externalities," and the potentiallyirreparable damage to fisheries because of mangrove loss has been greatly underestimated.